Pock marks in Glaze overpainting

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I fire to ^5, medium speed with 12 minute soak at end. Witness cones show an even heat throughout the kiln, yet I am getting pockmarks through an overpainting of Mayco Glaze & Coat when it is applied over a gloss white or gloss clear glaze. I have a picture of a piece before firing and 2 of the fired pieces. What causes this and how can I fix it? Thanks in advance for your responses! Steve

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I have used the Stroke & Coats successfully in cone 5 firing, but I only use 1 to 2 light coats over the glazed piece. Is it possible that the glaze was simply applied too thickly, with three coats of glaze and three coats of Stroke & Coat?

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Are you using a commercial white and clear, or one that you mix yourself? You might be getting a reaction between what is in the Mayco product and what is in your glaze. If you are using clear and white you mix yourself, check the Mayco site to see if they list any of the ingredients as problems/things to avoid (some underglazes don 't play well with zinc, for example).

Have you tried putting the underglaze on first, then applying clear over it? If so, did you get the same result?

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I have used the Stroke & Coats successfully in cone 5 firing, but I only use 1 to 2 light coats over the glazed piece. Is it possible that the glaze was simply applied too thickly, with three coats of glaze and three coats of Stroke & Coat?

This is a thinned out wash of Stroke and Coat color over a single dip of white or clear. Perhaps my dipped glaze is a bit thick.

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I have used the Stroke & Coats successfully in cone 5 firing, but I only use 1 to 2 light coats over the glazed piece. Is it possible that the glaze was simply applied too thickly, with three coats of glaze and three coats of Stroke & Coat?

This is a thinned out wash of Stroke and Coat over a dipped white or clear which may be too thick?

Share this post

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Are you using a commercial white and clear, or one that you mix yourself? You might be getting a reaction between what is in the Mayco product and what is in your glaze. If you are using clear and white you mix yourself, check the Mayco site to see if they list any of the ingredients as problems/things to avoid (some underglazes don 't play well with zinc, for example).

Have you tried putting the underglaze on first, then applying clear over it? If so, did you get the same result?

I will give underpainting first a try with a quick dip of the overglaze and I will check the commercial glaze recipe for zinc or other limitations. Thanks! But best of all, I am learning that it's not an application problem?